Pickup devices

ABSTRACT

An electrically conductive pickup for sensing electrically conductive areas on a moving flexible film comprising a fixed support curved in a plane normal to the surface of the film for effecting sliding contact therewith, and having at least two mutually insulated conductive surfaces spaced apart in the direction of the film width.

United States Patent 1,950,518 3/1934 Read [72] Inventor Bernard AlbertBentley Camberley, England 1 1 753,255

FOREIGN PATENTS 157,122 4/1952 Australia...................... 325,8451,099,843

9/1920 Germany... 2/1961 Germany......

827,551 2/1960 GreatBritain...........:::..

Primary Examiner-Louis R. Prince Assistant Examiner-Frederick ShoonAttorney-Holcombe, Wetherill & Brisebois [5 4] PICKUP DEVICES 5 Claims,4 Drawing Figs.

ABSTRACT: An electrically conductive pickup for sensing 22 m5 21 52 b 30 G [51] Int. [50]FieldofSearch............................................

electrically conductive areas on a moving flexible film comprising afixed support curved in a plane normal to the surface [56] Referencesand of the film for effecting sliding contact therewit UNITED STATES ATT at least two mutually insulated conductive su 4/1916 apart in thedirection ofthe film width.

h, and having rfaces spaced PATENTEU M3019?! SHEET 3 BF 3 The inventionrelates to electrically conductive pickup devices for sensing a movingflexible film.

The invention finds important application in the problem of designingkinematographic projection system which are required to initiateancillary functions such as the lowering of a safety curtain and thedimming and switching of auditorium lights. it is important that suchancillary functions be performed in a definite sequence whether priorto, during or after the actual film presentation and prior to theintroduction of noninflammable safety film such functions had to beperformed by means preferably independent of the film itself, and ingeneral because of the necessarily strict fire risk precautions forlimiting the permissible temperature rise of the film by means whichmaintain generated heat at an acceptable low level. For example, awell-known system of this kind includes a signal pickup associated withan idle film sprocket of the kinematograph projector, the pickup sensingelectrically conductive areas of the film formed by coatings, e.g., ofaluminum foil, stuck to the film. Such systems have been found to beobjectionable for various reasons. For example since the idle filmsprocket is rotating, slip-rings or equivalent devices are required forproviding continuity of the signal path from the pickup to an externalcontrol circuit. Secondly it is known that it is difiicult in practice,with a nondriven sprocket, to preserve continuous contact between thefilm and the surface of the sprocket, and hence also between theconductive surfaces of the pickup and the conductive areas of the film.This is because the inertia of the idle sprocket often causes it to lagslightly behind the film, this condition resulting in lack of registerbetween the holes in the film and the teeth of the idle sprocket. Randomfluttering and jumping of the film then results, which causes eitherpoor contact, or complete lack of contact between the conductive pickupsurfaces and the conductive areas of the film. This effect is aggravatedby the transfer to the sprocket of lacquer used to form a protectivelayer over the film emulsion. Transfer of even relatively minutequantities of lacquer form an insulating layer producing faultyoperation of the pickup.

Since however the ancillary functions are required to be performed in afixed sequence controlled by a sequence switching system, a fault or badcontact in the pickup device will result in a space instead of a mark inthe signal program, and hence in a faulty or out-of-phase sequence inthe switching control system which cannot later be corrected.

The purpose of the present invention is to provide an electricallyconductive pickup for sensing data on flexible film in the form ofelectrically conductive areas, e.g. strips, and especially a pickupwhich will remove the chief disadvantages of the known sprocket-typepickups used in film projectors.

Furthermore an object of the invention is to make it possible to derivefrom a flexible record carrier, bearing data in the form of conductiveareas, a series of signals in a predetermined sequence without risk ofinterruption or scrambling of the sequence.

in accordance with one aspect of the present invention these objects arebroadly achieved by an electrically conductive pickup device havingelectrically insulated conductive surfaces which are always fixed withreference to the moving film.

More particularly the invention consists in an electrically conductivepickup device for sensing recorded data in the form of conductive areason a moving flexible film, said pickup device including a fixed supportshaped to guide the film and having at least two mutually insulatedconducting surfaces spaced apart preferably in the direction of the filmwidth. The shape of the fixed support and the conducting surfaces aresuch that contact between such surfaces and the film is made over asufficient length of arc and at such a radius of curvature in a planenormal to the film surface as to avoid damage to the film or theconducting areas thereof.

An example of an electrically conductive pickup device according to theinvention suitable for use in sensing data cartied in kinematographicfilms will now be explained in more detail with reference to theaccompanying diagrammatic drawings, wherein:

FIG. 1 is a simplified diagram on an exaggerated scale of a crosssection of a film carrying recorded data in the form of electricallyconductive surfaces;

HO. 2 is an elevation partly in axial section of a pickup devicesuitable for sensing the film shown in FlG. 1;

H6. 3 is an end elevation;

FIG. 4 is an undersideview, partly in axial section, of the body of thepickup device.

Referring now to MG. 1, the emulsion area of the film representing theoptical record, for example the diapositive frames, is indicated at 1,whilst a sound. record carried adjacent one edge of the film, and whichmay be any of the known types of optical variable area or variabledensity or magnetic recordings, is shown at 2. On that side of the filmremote from the emulsion surface there are applied a convenient numberof very thin electrically conductive coatings 3, which may be depositedor applied in any suitable manner, for example stripes of metallic foil,e.g. of aluminum, bonded to the film by adhesive. Alternatively, knownchemical conducting compounds, of which stannous salts are an example,may be deposited.

Such electrically conductive surfaces may, as shown in the example,extend substantially acrossthe entire width of the film, but since thepurpose of the coating is to form a conducting bridge, such full widthdimension for the coating is not essential to the invention as will beapparent from the following description.

The electrically conductive sensing device indicated in FIGS. 2, 3, and4 comprises a body of metal 4, for example of hard chrome steel, havingat one end a flange 5 and three stepped zones 6, 7 and 8 of decreasingradius of curvature. Where, as in the example shown, the body is a majorpart of a generally cylindrical body of revolution, it may be machineturned from stock, the other end thereof having an integral spigot orshaft 9. Upon the shaft 9 there are mounted three metal segments 10, 11and 12 with intervening insulating spacing members l3, l4 and 15, forexample of the material known under the registered Trade Name Tufnol, toinsulate the segments from each other and from the body 4 of thesupport. Each of the segments 10, ll, 12 and the intervening insulatingspacers l3, l4, 15 are mounted upon the shaft 9 and held in position bya bonding medium for example the compound known under the Trade NameAraldite. insulated fixing screws 16 and 17 indicated in H68. 3 and 4are used to assemble the parts it) to H5 inclusive to the body of thepickup. The segments w, ll, 12 and the insulating spacers may initiallybe made in form of collars or bushes machined to size from stock andprovided with a bore to give them an interference fit over the shaft 9.After fitting has been completed the entire assembly may then bemachined along a plane parallel to the common axis to provide a planesurface whereby the body of the pickup may be mounted upon a basemounting plate 18 of insulating material which again may be of the samematerial as the spacers 133, M and 15, by means of screws 19 and 20. Thebase mounting plate is itself mounted upon a metal fixing plate 211 bymeans of screws 22.

Electrical connections to the electrically conductive insulated surfacesof the pickup are provided by screws such as 23 passing through the baseof the mounting plate and provided with terminal studs and nuts 25.

If desired a single electrical connection may be made in this manner toa common conductive surface formed by the stepped surfaces 6, 7 and 8 ofthe pickup, and individual conductive connections through separateterminals may be made to the segments 10, ii and 112, each of whichpresents a conductive surface individually insulated and insulated fromthe common conductive surface 65, 7, 8. The pickup device may be insalled in the appropriate position in a projector by means of an anglebracket (not shown), and in operation any one of three different widthsof film may be fitted in the respective grooves of the pickup device.For example, a standard film of the smallest width may be provided withConductive coatings, for example aluminum foil, to make bridging contactbetween the conductive flange 8 of the smallest radius and a conductivesurface 26 of the segment it).

It will be clear however that alternatively, or in addition, bridgingcontact may be similarly made between the surface of the collar 27 andthe surface 26.

With the larger sizes of film, bridging contact will be made between thestepped annular surfaces 7 and 6 respectively and the correspondinglyradiused parts of the conducting segments iii and iii, the largest widthof film being accommodated between the end flanges and 3% of the body ofthe support.

Obviously alternative arrangements are possible with a different spacingand arrangement of the conducting segments or collars it), ii and i2,and appropriate lengths of the conducting aluminum stripes on the film,the object being, in general, to obtain a sequence of signals due to thebridging over of insulated contact surfaces by conducting areas appliedto the surface of the film passing over the pickup device. Mostconveniently the control apparatus for controlling the sequence ofancillary functions comprises a sequence switch or stepping switchreceiving the pulses at the appropriate intervals from the pickup deviceat a given speed of the film. However, since the device is capable ofdelivering a sequence of pulses, a binary, or otherwise coded, countingcircuit with appropriate known storage and release facilities may beactuated to control the sequence of ancillary functions.

in the example shown in the drawing the body of the pickup device has astrictly cylindrical curvature making contact with the film over acircular arc. However, such shape is not essential and other geometricalforms of the contacting surfaces of the pickup device may be employedprovided that the area of mutual contact between the film and the pickupdevice is adequate to prevent snagging of the film and to promote smoothrunning and contact with the conducting surfaces of the pickup.

Although the example described employs metal, for example hard chrome,for the body of the pickup, it is nevertheless possible to make the bodyof the pickup of a different metal from the conducting surfaces, orwholly or partly of a suitable insulating material, e.g. a ceramic, uponwhich conductive coatings equivalent to the surfaces 6, 7 and 8 may bedeposited by plating or any other suitable process. A metal body ishowever preferred on account of ease of manufacture and ease of heatdissipation. Again the conducting pickup areas may be deposits of noblemetal, e.g., rhodium or platinum upon an intermediate plating metal. Thesurfaces of the parts ll), 11 etc. are finished to reduce to a minimumfriction and consequent heat generation as a result of contact with thefilm. To this end, the insulating spacers l3 and 14 are undercut withrespect to their adjacent surfaces, so as to prevent contact with thefilm and thereby further reduce frictional losses.

lclaim:

1. An electrically conductive pickup for sensing electrically conductiveareas on a moving flexible film comprising a fixed support shaped toguide the moving film, said support having at one side a firstconductive surface making contact with a marginal strip of the filmsurface, and having at the other side of the support a plurality ofconducting surfaces mutually insulated from each other and from thefirst conductive surface, said plurality of conductive surfaces beingspaced apart in the direction of the film width, whereby conductivecontact can be established by bridging said first conductive surface andone or more of said plurality of conductive surfaces by conductivestrips of various dimensions in the width of the film, and wherein saidsupport is of stepped formation to present arcuate flanges forming filmcontacting surfaces which are of decreasing radii of curvature in planeswhich lie normal to the film surface and parallel to the direction ofmotion of the film and which are of decreasin dimension in the directionof the film width, whereby films of different width may be supported andcontacted by pairs of flanges contacting longitudinal marginal zones ofsaid film at opposite edges thereof, intervening portions of saidsupport being undercut to prevent contact with said film surface exceptat said conductive surfaces of the support.

2. An electrically conductive pickup for sensing electrically conductiveareas on a moving flexible film comprising a fixed support shaped toguide the moving film, said support having at one side a firstconductive surface making contact with a marginal strip of the filmsurface, and having at the other side of the support a plurality ofconducting surfaces mutually insulated from each other and from thecommon conductive surfaces, said plurality of conductive surfaces beingspaced apart in the direction of the film width, whereby conductivecontact can be established by bridging said first conductive surface andone or more of said plurality of conductive surfaces by conductivestrips of various dimensions in the width ofthe film, and wherein thefirst conductive surface at said one side of the support is stepped todecreasing radii of curvature towards the center of the film, andwherein the support is similarly stepped for each of said plurality ofconductive surfaces at the other side of the support, whereby films ofdifferent width may be guided between said respective steps to makebridging contact between said first conducting surface and one of saidplurality of conducting surfaces.

3. An electrically conductive pickup as claimed in claim 2, wherein thebody of the support is of electrically conductive material and theplurality of conductive surfaces are formed by electrically conductivesegments having segments of insulating material intervening to insulatethem from each other and from said first conductive surface.

4. An electrically conductive pickup as claimed in claim 2, wherein thebody of the support is of electrically conductive material and theplurality of conductive surfaces are formed by electrically conductivesegments having segments of insulating material intervening to insulatethem from each other and from said first conductive surface, and whereinthe intervening insulation is formed by a mass of cast resin.

5. An electrically conductive pickup device as claimed in claim 2,wherein the body of the support is of electrically conductive materialand the plurality of conductive surfaces are formed by electricallyconductive segments having segments of insulating material interveningto insulate them from each other and from said first conductive surface,and wherein the intervening insulation is performed by machining fromstock.

1. An electrically conductive pickup for sensing electrically conductiveareas on a moving flexible film comprising a fixed support shaped toguide the moving film, said support having at one side a firstconductive surface making contact with a marginal strip of the filmsurface, and having at the other side of the support a plurality ofconducting surfaces mutually insulated from each other and from thefirst conductive surface, said plurality of conductive surfaces beingspaced apart in the direction of the film width, whereby conductivecontact can be established by bridging said first conductive surface andone or more of said plurality of conductive surfaces by conductivestrips of various dimensions in the width of the film, and wherein saidsupport is of stepped formation to present arcuate flanges forming filmcontacting surfaces which are of decreasing radii of curvature in planeswhich lie normal to the film surface and parallel to the direction ofmotion of the film and which are of decreasing dimension in thedirection of the film width, whereby films of different width may besupported and contacted by pairs of flanges contacting longitudinalmarginal zones of said film at opposite edges thereof, interveningportions of said support being undercut to prevent contact with saidfilm surface except at said conductive surfaces of the support.
 2. Anelectrically conductive pickup for sensing electrically conductive areason a moving flexible film comprising a fixed support shaped to guide themoving film, said support having at one side a first conductive surfacemaking contact with a marginal strip of the film surface, and having atthe other side of the support a plurality of conducting surfacesmutually insulated from each other and from the common conductivesurfaces, said plurality of conductive surfaces being spaced apart inthe direction of the film width, whereby conductive contact can beestablished by bridging said first conductive surface and one or more ofsaid plurality of conductive surfaces by conductive strips of variousdimensions in the width of the film, and wherein the first conductivesurface at said one side of the support is stepped to decreasing radiiof curvature towards the center of the film, and wherein the support issimilarly stepped for each of said plurality of conductive surfaces atthe other side of the support, whereby films of different width may beguided between said respective steps to make bridging contact betweensaid first conducting surface and one of said plurality of conductingsurfaces.
 3. An electrically conductive pickup as claimed in claim 2,wherein the body of the support is of electrically conductive materialand the plurality of conductive surfaces are formed by electricallyconductive segments having segments of insulating material interveningto insulate them from each other and from said first conductive surface.4. An electrically conductive pickup as claimed in claim 2, wherein thebody of the support is of electrically conductive material and theplurality of conductive surfaces are formed by electrically conductivesegments having segments of insulating material intervening to insulatethem from each other and from said first conductive surface, and whereinthe intervening insulation is formed by a mass of cast resin.
 5. Anelectrically conductive pickup device as claimed in claim 2, wherein thebody of the support is of electrically conductive material and theplurality of conductive surfaces are formed by electrically conductivesegments having segments of insulating material intervening to insulatethem from each other and from sAid first conductive surface, and whereinthe intervening insulation is performed by machining from stock.